The present invention relates to a piezoelectric composite device, a method of manufacturing the same, a method of controlling the same, an input-output device, and an electronic device that are suitable for application to portable telephones, digital cameras, portable terminals, remote controllers and the like having a tactile input function.
The present invention relates particularly to a piezoelectric composite device including a first piezoelectric element joined between a feeding electrode and a common electrode; and a second piezoelectric element joined between the common electrode and a signal detecting electrode; wherein a predetermined voltage is supplied between the feeding electrode and the common electrode, and a force detection signal based on an external force is extracted from the detecting electrode, so that the piezoelectric composite device can be provided which combines a piezoelectric bimorph type actuator vibrating on the basis of the predetermined voltage supplied between the feeding electrode and the common electrode with a force detecting sensor outputting the force detection signal based on the external force.
There have recently been more and more cases where users (operators) use a digital camera having multiple operation modes to photograph a subject, and capture various contents into a portable terminal such as a portable telephone, a PDA (Personal Digital Assistant) or the like and use the various contents. The digital camera and the portable terminal and the like have an input-output device. A touch panel that combines input section such as a keyboard, various keys, a JOG dial and the like with a display unit, for example, is often used for the input-output device.
In addition, an input-output device combined with an actuator has been developed. In the actuator, piezoelectric elements having different amounts of distortion in two or more layers, or piezoelectric elements and a non-piezoelectric element are bonded to each other, and a bend deformation of the bonded object which deformation is caused by a difference in the amounts of distortion of both the elements when a voltage is applied to the piezoelectric elements is used dynamically. So-called bimorph actuators, unimorph actuators, disk actuators and the like (hereinafter referred to collectively as piezoelectric bimorph type actuators) are often used as the actuator.
FIG. 26 is a perspective view of an example of structure of a multilayer piezoelectric bimorph type actuator 300 according to a conventional example. The multilayer piezoelectric bimorph type actuator 300 shown in FIG. 26 is formed by bonding together laminated piezoelectric substance groups 4a and 4b that elongate and contract respectively in opposite directions to each other on both sides of a central electrode 13 as a neutral surface of bend deformation. A metal sheet of stainless steel or the like is generally used for the central electrode 13. Leads L1 and L2 are connected to the central electrode 13 and an upper part surface electrode 11 or a lower part surface electrode 12. The upper part surface electrode 11 and the lower part surface electrode 12 are used in a state of being short-circuited by a short-circuit line L0. The actuator 300 is characterized by allowing lower-voltage driving as compared with a single-layer piezoelectric actuator.
FIG. 27 is a sectional view showing an example of a laminated structure of the multilayer piezoelectric bimorph type actuator 300. FIG. 27 is a sectional view taken along a line Y1-Y2 of FIG. 26 showing the actuator 300. The multilayer piezoelectric bimorph type actuator 300 shown in FIG. 27 has the laminated piezoelectric substance group 4a and the laminated piezoelectric substance group 4b. Piezoelectric elements within the same laminated piezoelectric substance group 4a deform in the same direction, and piezoelectric elements within the same laminated piezoelectric substance group 4b deform in the same direction. The laminated piezoelectric substance group 4a and the laminated piezoelectric substance group 4b deform in opposite directions to each other. The actuator 300 thereby performs bend deformation. In order to drive the actuator 300, power is supplied with the surface electrodes (upper and lower) 11 and 12 at outermost surfaces short-circuited and with the leads L1 and L2 connected to the upper part surface electrode 11 or the lower part surface electrode 12 and the central electrode 13, as shown in FIG. 26.
The actuator 300 can be used as a force detecting sensor as reverse action of the actuator 300. In this case, a voltage generated by a deformation of the actuator 300 due to an external force is taken out from the above-mentioned leads L1 and L2 to the outside. Each of the laminated piezoelectric substance groups 4a and 4b includes piezoelectric elements in the form of layers and internal electrode layers (main electrodes) IE1 to IE16 formed such that the piezoelectric elements are sandwiched between the internal electrode layers IE1 to IE16. These internal electrode layers IE1 to IE16 are connected within the actuator. Generally, in this internal connection, alternate layers are connected to each other by a method using via holes or an actuator side part formed with the internal electrodes exposed, for example, and the piezoelectric elements are used in electrically parallel connection with each other. The internal connection cannot be changed from the outside. This is because the internal connection is not drawn out to the outside of the actuator.
In relation to an electronic device having this kind of piezoelectric actuator, for example, in Japanese Patent Laid-Open No. 2004-94389 (pages 4 and 5, FIG. 11) (hereinafter referred to as Patent Document 1), discloses an input-output device and an electronic device. This electronic device includes an input-output device having a multilayer piezoelectric bimorph type actuator and a touch panel. The multilayer piezoelectric bimorph type actuator feeds back a different tactile sense to a user through the touch panel according to a type of information. The electronic device being thus formed, when the user performs an input operation on the touch panel using the sense of touch, a tactile feedback in response to the input operation in accordance with a type of information can be surely provided to the user.